Add a unit test that I have laying around

Weird, no idea why this isn't in Git and where it should have been committed...

Signed-off-by: Uli Schlachter <psychon@znc.in>

spec/wibox/widget/base_spec.lua

@@ -0,0 +1,53 @@
+---------------------------------------------------------------------------
+-- @author Uli Schlachter
+-- @copyright 2016 Uli Schlachter
+---------------------------------------------------------------------------
+
+local base = require("wibox.widget.base")
+local no_parent = base.no_parent_I_know_what_I_am_doing
+
+describe("wibox.widget.base", function()
+    local widget1, widget2
+    before_each(function()
+        widget1 = base.make_widget()
+        widget2 = base.make_widget()
+        widget1.layout = function()
+            return { base.place_widget_at(widget2, 0, 0, 1, 1) }
+        end
+    end)
+
+    describe("caches", function()
+        it("garbage collectable", function()
+            local alive = setmetatable({ widget1, widget2 }, { __mode = "kv" })
+            assert.is.equal(2, #alive)
+
+            widget1, widget2 = nil, nil
+            collectgarbage("collect")
+            assert.is.equal(0, #alive)
+        end)
+
+        it("simple cache clear", function()
+            local alive = setmetatable({ widget1, widget2 }, { __mode = "kv" })
+            base.layout_widget(no_parent, { "fake context" }, widget1, 20, 20)
+            assert.is.equal(2, #alive)
+
+            widget1, widget2 = nil, nil
+            collectgarbage("collect")
+            assert.is.equal(0, #alive)
+        end)
+
+        it("self-reference cache clear", function()
+            widget2.widget = widget1
+
+            local alive = setmetatable({ widget1, widget2 }, { __mode = "kv" })
+            base.layout_widget(no_parent, { "fake context" }, widget1, 20, 20)
+            assert.is.equal(2, #alive)
+
+            widget1, widget2 = nil, nil
+            collectgarbage("collect")
+            assert.is.equal(0, #alive)
+        end)
+    end)
+end)
+
+-- vim: filetype=lua:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:textwidth=80